A commonly known type of switch used on circuit boards comprises a generally rectangular housing assembly having a plurality of individual switches therein. Each switch serves to connect two circuit board conductors and has a slide member therein which changes the condition of the switch whenever the slide member is moved from one position to another position. Switches of this type are commonly referred to as DIP switches for the reason that they ideally should have the same dimensions as a standard dual-in-line package of the class used for packaging integrated circuits or the like.
The standard width for a DIP switch is about 0.276 inches and the length of the switch will depend upon the number of switch units contained in the assembly. The length of each switch unit should be about 0.100 inches in order that it will conform to standard circuit board conventions.
One type of DIP switch has a rockable contact bar for each switch unit which is pivoted on one of the switch conductors in the switch assembly and which is rocked between first and second positions to change the condition of the switch. The bar is pivoted on one of the switch conductors so that in one position, it electrically connects the two switch conductors in the switch unit and in the other position, the conductors are not connected to each other. The rockable contact bar is rocked by means of a spring contained in a slide housing which forms part of the DIP switch housing assembly. The provision of the spring poses one of the most troublesome problems in the design of DIP switches for the reason that the spring must be very small but at the same time the force with which the spring bears against the contact bar must be precisely controlled. This force should not be unduly high for the reason that if it is, the switch will wear out in a very short time because of abrasion. On the other hand, the force exerted must be sufficient to establish good contact when the switch is closed. Also, the spring should be as small as reasonably possible particularly as regards its height so that the overall height of the DIP switch assembly, including the housing assembly, will not greatly exceed the standard dimensions of a conventional dual-in-line package of an integrated circuit.
U.S. Pats. Nos. 4,191,867, 4,531,030, 4,311,884, and 4,268,728 disclose different approaches to the DIP switch design problem. U.S. Pat. No. 4,531,030 shows a widely used type of DIP switch in which the spring is a bellows spring having several bellows spring sections, one of which bears against the rockable contact bar and the other one of which bears against an interior wall of the switch housing. In many respects, a bellows spring is ideally suited for use in DIP switches for the reason that its contact force can be accurately controlled and will not be unduly high. It would be desirable, however, to reduce the overall height of the type of DIP switch shown in the above-identified U.S. Pat. No. 4,531,030 while retaining the advantages of a bellows spring. The present invention is directed to the achievement of an improved DIP switch having a bellows spring means which permits a substantial reduction in the overall height of the DIP switch assembly and which achieves other advantages as will be explained below.